#include <iostream>
#include <string>
using namespace std;

#define ENCODE 7

int R, C;

string recorEspiral(const string& entrada) {
    string recorrido = "";
    int sup = 0, izq = 0, inf = R-1, der = C-1, i, j;
    while (sup <= inf && izq <= der) {
        i = sup;
        j = izq;
        while (j < der)
            recorrido += entrada[i*C+j++]-ENCODE;
        if (sup == inf) {
            recorrido += entrada[i*C+j++]-ENCODE; break; }
        while (i < inf)
            recorrido += entrada[i++*C+j]-ENCODE;
        if (izq == der) {
            recorrido += entrada[i++*C+j]-ENCODE; break; }
        while (j > izq)
            recorrido += entrada[i*C+j--]-ENCODE;
        while (i > sup)
            recorrido += entrada[i--*C+j]-ENCODE;
        sup++; izq++; inf--; der--;
    }
    return recorrido;
}

int main() {
    string entrada;
    while (cin >> R >> C && !(R==0 && C==0)) {
        cin >> entrada;
        cout << recorEspiral(entrada) << endl;
    }
    return 0;
}